Conventionally, a copper electric wire is typically used as a wire harness routed in a vehicle or the like because of its good electrical conductivity. However, recently, a demand for replacing the copper electric wire with an aluminum electric wire has been increased in view of low weight, good fuel economy owing to the low weight, and recycle of metal resources in addition to a lack of copper resources, and price increase due to the lack of copper resources.
Because aluminum has high electric conductivity next to copper, and good workability for wire drawing, and is lightweight (specific gravity is one third of that of copper), conventionally, aluminum is used as electric wire material mainly in use of aerial power cable, aerial distribution line, or the like.
Here, as an exemplary aluminum wire, an aluminum wire only composed of stranded aluminum element wire or stranded aluminum alloy wire, and an aluminum wire composed of stranded copper coated aluminum wire (for example, see Patent Document 1) are known.
However, conventional aluminum wire composed of aluminum element wire or aluminum alloy element wire is not suitable for in-vehicle environment. Namely, in vehicle environment, high strength against bending or pulling of the wire is required because of the necessity of routing the wire in a limited space, however, the aluminum wire having less strength than the copper wire is limited in a range of application of in-vehicle environment in view of environmental resistance (high temperature, high humidity, bending, pulling, or the like).
Therefore, for solving these problems, a composite electric wire having aluminum element wire in a center portion, and molten aluminum coated iron wire in its surrounding portion is proposed (for example, see Patent Document 2).
Further, steel core aluminum stranded wire composed of steel stranded wire in a center portion and aluminum stranded wire in its surrounding portion, and steel core aluminum stranded wire composed of invar stranded wire instead of steel wire are known (for example, see Patent Document 3).    Patent Document 1: JP, A, H11-181593    Patent Document 2: JP, A, 2006-339040    Patent Document 3: JP, A, 2000-90744